Determination of Force Exerted During Pull Test

ABSTRACT

Aim:

The aim of this was to determine the force exerted during the pull test using a hand-held spring balance.

Materials and Methods:

A hand-held spring balance was used to determine the force exerted during pull test. Ten volunteers performed the test five times each, and the mean was recorded as the force exerted by each volunteer.

Results:

A total of 10 volunteers were included in the study. The mean value of the force exerted by the volunteers was 0.25 N (Newton).

Conclusion:

Using the spring balance, we attempted to measure the force used while performing the pull test, which may help in standardizing the hair pull test. Further experiments are being undertaken to determine the grasping force exerted during pull test. These two forces when combined in an instrument will enable us to overcome the individual investigator variability while performing the test.

INTRODUCTION

Hair loss is a frequently encountered problem and is evaluated by various simple and noninvasive clinical hair tests. The most common test performed for the clinical assessment of hair loss is the hair pull test, which involves grasping a bundle of hair and then gently pulling the hair from the scalp.[1] If >10% of hair is epilated, the test is considered positive.[1] However, this test is not standardized and hence the force applied while pulling the hair is likely to vary with each investigator. Using a spring balance, we tried to determine the force exerted during the pull test.

MATERIALS AND METHODS

It is a noninterventional, single-group standardization of scores study. A hand-held spring balance which was 16 cm long with a diameter of 3 cm with acrylic tubular barrel and capacity of 100 g (g)/1 newton (N) was used [Figure 1].

Figure 1.

Hand-held spring balance

A bunch of 50–60 hair was collected and the proximal end of the hair containing the hair root was tied using a string, and the other end of the string was tied to the hook of the spring balance [Figure 2]. The bundle of hair was wiped to remove dirt, scales, and oil. The spring balance was held against the wall by the investigator at the eye level, [Figure 2], and 10 volunteers were asked to pull the hair bundle that was attached to the spring balance by grasping the proximal end of hair between the thumb, index, and middle finger, and gently sliding from the proximal to the distal end of hair simulating the hair pull test [Video 1]. During this process, simultaneously, along the inner surface of the spring balance, the force indicator slides down and halts appropriately at the level when the fingers reach the distal end of the hair after which the fingers slide away from the hair [Video 1]. The force exerted during this technique of pull test using a hand-held spring balance was recorded in newton (N).

Figure 2.

Hair attached to the hand-held spring balance

Ten volunteers performed the test. Each volunteer performed the test five times, and the mean was taken as the force exerted in newton (N) [Table 1].

Table 1.

Force exerted by 10 volunteers during pull test

Investigators	Force in newton (n) during each pull test	Total force in newton (n)	Mean value (n)
1	0.18	0.98	0.20
	0.20
	0.21
	0.20
	0.19
2	0.24	1.15	0.23
	0.24
	0.20
	0.23
	0.24
3	0.27	1.27	0.25
	0.25
	0.27
	0.24
	0.24
4	0.29	1.32	0.26
	0.27
	0.24
	0.27
	0.25
5	0.28	1.23	0.25
	0.25
	0.22
	0.23
	0.25
6	0.25	1.22	0.24
	0.24
	0.25
	0.23
	0.25
7	0.29	1.41	0.28
	0.28
	0.29
	0.26
	0.29
8	0.24	1.37	0.27
	0.25
	0.28
	0.29
	0.31
9	0.25	1.28	0.26
	0.24
	0.25
	0.27
	0.27
10	0.29	1.36	0.27
	0.26
	0.29
	0.27
	0.25

RESULTS

Ten volunteers were included, and the force exerted by each volunteer is shown in Table 1. The mean value of the force exerted by the total of 10 volunteers was 0.25 N.

DISCUSSION

Hair loss is a natural event resulting in the shedding of 80–100 telogen hairs per day in a healthy individual.[2] The etiology of hair loss is multifactorial, and it is broadly classified as physiological and pathological. Several techniques are available to assess a patient with hair loss such as hair pull test, trichogram (hair pluck test), phototrichogram, unit area trichogram, digital phototrichogram, trichotillometry, hair diameter assessment, dermoscopy, and scalp biopsy.[1,3] A hand-held trichotillometer is used to determine the epilation force required to pluck the hair among healthy volunteers.[3]

The hair pull test is also called the “traction test” or the “pull-out sign or Sabouraud’s sign.”[4] This test helps in evaluating the location and severity of hair loss, and is performed by the concept of “gentle” pulling of hair which causes the shedding of telogen hair.[5] This test is performed by grasping a bundle of about 50–60 adjacent hair in a particular region close to the scalp using the thumb, index finger, and middle finger.[6] The investigator then gently pulls on the hair bundle by administering slow traction, and avoiding a forceful tug while the fingers are moved down the hair shaft.[5] This hair pull test is considered positive if >10% of hair in the hair bundle is epilated from the scalp.[7]

Although this technique is frequently used, it has its own limitations such as lack of validation of the test, pretest hair brushing and hair washing guidelines, and accountability of the hair texture. Since each individual is likely to grasp and pull the hair using different forces, there is likely to be significant interobserver variability. Due to this interindividual variation, standardization of this technique may be helpful. This study is an attempt to measure the force used during the act of pulling the hair and does not address the pressure applied by the individual examiner while grasping the hair.

Limitations

Limitations of our study are that other hair parameters such as hair density and diameter, shape, hair growth rate, composition, and mechanical properties were not assessed. This study only determines the force exerted while performing the pull test. It, however, does not address the pressure applied by the individual investigator while grasping the hair.

CONCLUSION

Using the spring balance, we attempted to assess the force used while performing the pull test. This technique may help in standardizing the hair pull test. Studies are on to find/fabricate equipment to standardize the pinch force or the force exerted while grasping the hair. These two forces when combined in an instrument will enable us to overcome the individual investigator variability while performing the test.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.